From 73172345f73fab9549258203e1efcdc5a921d460 Mon Sep 17 00:00:00 2001
From: Slava Pestov <spestov@apple.com>
Date: Wed, 13 Feb 2019 19:16:46 -0500
Subject: [PATCH] ASTMangler: Fix mangling of type aliases in fully-constrained
 extensions

We should still mangle these as generic types.

Fixes <rdar://problem/47980487>.
---
 lib/AST/ASTMangler.cpp         | 2 +-
 test/DebugInfo/typealias.swift | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/AST/ASTMangler.cpp b/lib/AST/ASTMangler.cpp
index 4fc2e873834c3..cd7ea4224dacc 100644
--- a/lib/AST/ASTMangler.cpp
+++ b/lib/AST/ASTMangler.cpp
@@ -793,7 +793,7 @@ void ASTMangler::appendType(Type type) {
         return appendType(aliasTy->getSinglyDesugaredType());
       }
 
-      if (aliasTy->getSubstitutionMap().hasAnySubstitutableParams()) {
+      if (aliasTy->getSubstitutionMap()) {
         // Try to mangle the entire name as a substitution.
         if (tryMangleTypeSubstitution(tybase))
           return;
diff --git a/test/DebugInfo/typealias.swift b/test/DebugInfo/typealias.swift
index 25f3c8750cef1..7ffab3479cf5c 100644
--- a/test/DebugInfo/typealias.swift
+++ b/test/DebugInfo/typealias.swift
@@ -101,3 +101,10 @@ public func usesGeneric(y: (GenericAlias<Int>, GenericClass<Int>, GenericAlias<I
   let x = y
   markUsed(x)
 }
+
+public struct Ox<T> {}
+extension Ox where T == Int {
+  public typealias Plow = Int
+}
+
+var v: Ox<Int>.Plow = 0
\ No newline at end of file